Integrated Electrochemical Biosensors for Detection of Waterborne Pathogens in Low-Resource Settings

More than 783 million people worldwide are currently without access to clean and safe water. Approximately 1 in 5 cases of mortality due to waterborne diseases involve children, and over 1.5 million cases of waterborne disease occur every year. In the developing world, this makes waterborne diseases the second highest cause of mortality. Such cases of waterborne disease are thought to be caused by poor sanitation, water infrastructure, public knowledge, and lack of suitable water monitoring systems. Conventional laboratory-based techniques are inadequate for effective on-site water quality monitoring purposes. This is due to their need for excessive equipment, operational complexity, lack of affordability, and long sample collection to data analysis times. In this review, we discuss the conventional techniques used in modern-day water quality testing. We discuss the future challenges of water quality testing in the developing world and how conventional techniques fall short of these challenges. Finally, we discuss the development of electrochemical biosensors and current research on the integration of these devices with microfluidic components to develop truly integrated, portable, simple to use and cost-effective devices for use by local environmental agencies, NGOs, and local communities in low-resource settings

Electrochemical behavior of quercetin on boron-doped diamond electrode in different supporting electrolytes

Quercetin is one of the most abundant flavonoid compounds with a broad spectrum of health beneficial properties. In this study electrochemical behavior of quercetin on boron-doped diamond electrode as a working electrode was investigated in different supporting electrolytes. Experiments embraced 0.1 mol/L acetate buffer, citrate buffer, phosphate buffer, 0.04 mol/L Britton-Robinson buffer and 0.05 mol/L solution of HCl, while studied quercetin concentration were in the range from 2 mg/L to 30 mg/L. Voltammograms recorded in different supporting electrolytes revealed one sharp and well-defined oxidation peak of quercetin at the potential of about +0.70 V, and it was chosen for quantification of quercetin, although in some buffers one additional protracted peak was observed. In comparison to differential pulse voltammetry, square-wave voltammetry showed higher sensitivity, so this technique could be more suitable for further development. Even though high values of correlation coefficients (> 0.9900) were obtained for all studied supporting electrolytes, the best results in terms of sensitivity were observed for citrate and Britton-Robinson buffers. These preliminary results demonstrated that boron-doped diamond electrode can be used as a sensitive sensor for precise determination of quercetin in real samples

The Application of Curve Fitting on the Voltammograms of Various Isoforms of Metallothioneins–Metal Complexes

The translation of metallothioneins (MTs) is one of the defense strategies by which organisms protect themselves from metal-induced toxicity. MTs belong to a family of proteins comprising MT-1, MT-2, MT-3, and MT-4 classes, with multiple isoforms within each class. The main aim of this study was to determine the behavior of MT in dependence on various externally modelled environments, using electrochemistry. In our study, the mass distribution of MTs was characterized using MALDI-TOF. After that, adsorptive transfer stripping technique with differential pulse voltammetry was selected for optimization of electrochemical detection of MTs with regard to accumulation time and pH effects. Our results show that utilization of 0.5 M NaCl, pH 6.4, as the supporting electrolyte provides a highly complicated fingerprint, showing a number of non-resolved voltammograms. Hence, we further resolved the voltammograms exhibiting the broad and overlapping signals using curve fitting. The separated signals were assigned to the electrochemical responses of several MT complexes with zinc(II), cadmium(II), and copper(II), respectively. Our results show that electrochemistry could serve as a great tool for metalloproteomic applications to determine the ratio of metal ion bonds within the target protein structure, however, it provides highly complicated signals, which require further resolution using a proper statistical method, such as curve fitting.The work has been supported by the Agency for the Czech Republic Health Research (AZV) project no. 15-28334A. The presented research was financed by the Czech Ministry of Education in frame of the National Sustainability Program, the grant LO1401 INWITE

Determination of Zinc, Cadmium, Lead, Copper and Silver Using a Carbon Paste Electrode and a Screen Printed Electrode Modified with Chromium(III) Oxide

In this study, the preparation and electrochemical application of a chromium(III) oxide modified carbon paste electrode (Cr-CPE) and a screen printed electrode (SPE), made from the same material and optimized for the simple, cheap and sensitive simultaneous determination of zinc, cadmium, lead, copper and the detection of silver ions, is described. The limits of detection and quantification were 25 and 80 mu g center dot L-1 for Zn(II), 3 and 10 mu g center dot L-1 for Cd(II), 3 and 10 mu g center dot L-1 for Pb(II), 3 and 10 mu g center dot L-1 for Cu(II), and 3 and 10 mu g center dot L-1 for Ag(I), respectively. Furthermore, this promising modification was transferred to the screen-printed electrode. The limits of detection for the simultaneous determination of zinc, cadmium, copper and lead on the screen printed electrodes were found to be 350 mu g center dot L-1 for Zn(II), 25 mu g center dot L-1 for Cd(II), 3 mu g center dot L-1 for Pb(II) and 3 mu g center dot L-1 for Cu(II). Practical usability for the simultaneous detection of these heavy metal ions by the Cr-CPE was also demonstrated in the analyses of wastewaters

In situ investigation of the cytotoxic and interfacial characteristics of titanium when galvanically coupled with magnesium using scanning electrochemical microscopy

Recently, the cytotoxic properties of galvanically coupled Mg-Ti particles have been shown to different cells, although this cytotoxic effect has been attributed mainly to Mg due to its tendency to undergo activation when coupled with Ti forming a galvanic cell consisting of an anode (Mg) and a cathode (Ti). However, the role of the Ti cathode has been ignored in explaining the cytotoxic effect of Mg-Ti particles due to its high resistance to corrosion. In this work, the role of titanium (Ti) in the cytotoxic mechanism of galvanically coupled Mg-Ti particles was examined. A model galvanic cell was prepared to simulate the Mg-Ti particles. The electrochemical reactivity of the Ti sample and the pH change above it due to galvanic coupling with Mg were investigated using scanning electrochemical microscopy (SECM). It was observed that the Ti surface changed from passive to electrochemically active when coupled with Mg. Furthermore, after only 15 min galvanic coupling with Mg, the pH in the electrolyte volume adjacent to the Ti surface increased to an alkaline pH value. The effects of the galvanic coupling of Ti and Mg, as well as of the alkaline pH environment, on the viability of Hs27 fibroblast cells were investigated. It was shown that the viability of Hs27 cells significantly diminished when Mg and Ti were galvanically coupled compared to when the two metals were electrically disconnected. Next, the generation of reactive oxygen species (ROS) increased when the Ti and Mg were galvanically coupled. Thus, although Ti usually exhibited high corrosion resistance when exposed to physiological environments, an electrochemically active surface was observed when galvanically coupled with Mg, and this surface may participate in electron transfer reactions with chemical species in the neighboring environment; this participation resulted in the increased pH values above its surface and enhanced generation of ROS. These features contributed to the development of cytotoxic effects by galvanically coupled Mg-Ti particles

LiYbCl4(THF)4

The title compound, di-μ-chlorido-dichlorido-1κ2Cl-tetrakis(tetrahydrofuran)-1κ2O,2κ2O-lithiumytterbium(III), [LiYbCl4(C4H8O)4], was prepared by the reaction of YbCl3(THF)3 with LiCl in THF (THF is tetrahydrofuran). The central motif of the structure is a Yb(μ-Cl)2Li ring. The Yb atom is hexacoordinated to four Cl atoms and two THF molecules oriented in a trans fashion. The Li atom has a tetrahedral environment and is coordinated to two Cl atoms and two THF molecules. No intermolecular interactions other than van der Waals forces were observed. Two of the THF molecules are disordered over two positions

New trends in methyl salicylate sensing and their implications in agriculture

Methyl salicylate (MeSal) is an organic compound present in plants during stress events and is therefore a key marker for early plant disease detection. It has usually been detected by conventional methods that require bulky and costly equipment, such as gas chromatography or mass spectrometry. Currently, however, chemical sensors provide an alternative for MeSal monitoring, showing good performance for its determination in the vapour or liquid phase. The most promising concepts used in MeSal determination include sensors based on electrochemical and conductometric principles, although other technologies based on mass-sensitive, microwave, or spectrophotometric principles also show promise. The receptor elements or sensitive materials are shown to be part of the key elements in these sensing technologies. A literature survey identified a significant contribution of bioreceptors, including enzymes, odourant-binding proteins or peptides, as well as receptors based on polymers or inorganic materials in MeSal determination. This work reviews these concepts and materials and discusses their future prospects and limitations for application in plant health monitoring

Electrochemical Evaluation of Selenium (IV) Removal from Its Aqueous Solutions by Unmodified and Modified Graphene Oxide

The removal of selenium from superficial and waste water is a worldwide problem. The maximum limit according to the World Health Organization (WHO) for the selenium in the water is set at a concentration of 10 μg/L. Carbon based adsorbents have attracted much attention and recently demonstrated promising performance in removal of selenium. In this work, several materials (iron oxide based microparticles and graphene oxides materials) and their composites were prepared to remove Se(IV) from water. The graphene oxides were prepared according to the simplified Hummer’s method. In addition, the effect of pH, contact time and initial Se(IV) concentration was tested. An electrochemical method such as the differential pulse cathodic stripping voltammetry was used to determine the residual selenium concentration. From the experimental data, Langmuir adsorption model was used to calculate the maximum adsorption capacity. Graphene oxide particles modified by iron oxide based microparticles was the most promising material for the removal of Se(IV) from its aqueous solution at pH 2.0. Its adsorption efficiency reached more than 90% for a solution with given Se(IV) concentration, meanwhile its maximal recorded adsorption capacity was 18.69 mg/g